When compared to different commercially available operating systems, Linux’s best assets are its price and its reliability. With the latest 2.6 Linux kernel, you can also argue that scalability is one of its greatest assets.
Most people know that its initial price is free (or at least under $50 when it comes in a box or with a book). However, when people talk about Linux’s affordability, they are usually thinking of its total cost, which includes no (or low) licensing fees and the capability of using inexpensive hardware and compatible free add-on applications. Although commercial operating systems tend to encourage upgrading to later hardware, Linux doesn’t (although faster hardware and larger disks are nice to have).
In terms of reliability, the general consensus is that Linux is comparable to many commercial UNIX systems but more reliable than most desktop-oriented operating systems. This is especially true if you rely on your computer system to stay up because it is a Web server or a file server. (You don’t have to reboot every time you change something.)
Another advantage of using Linux is that help is always available on the Internet. There is probably someone out there in a Linux newsgroup or mailing list willing to help you get around your problem. Because the source code is available, if you need something fixed you can even patch the code yourself! On the other hand, I’ve seen commercial operating system vendors sit on reported problems for months without fixing them. Remember that the culture of Linux is one that thrives on people helping other people.